Well, I am not fit for dabbling in the literature of theoretical linguistics but, if my fleeting memory serves anything, linguists regard the object to teach (or maybe the person to teach as well) as a overt (or morphological) accusative with a covert (or functional) case other than accusative.

A phenomenon to justify such a treatment in Latin would be subordinate clauses whose verb is infinitive. In "audio Cleopatram Antonium amavisse (I hear Cleopatra loved Antonius or I hear Antonius loved Cleopatra)," both of the nouns are in accusative, whereas the argument structure of the verb "amo" claims an Agent and a Patient. In a simplex Latin sentence whose verb is "amo," Agent nouns assume nominative, and Patient nouns accusative. In my compound clause above, the nouns are interpreted as serving as Agent and Patient, thus functionally in nominative and accusative, though which noun assumes which role is not all together clear grammatically.

As for your German example, BD, I am wondering if replacing "etwas" with a noun with the definite article in accusative is possible.

Your comment about the accusative subject is perfect, it never occurred to me that there could be an analogy between that and the verb docere.

As for your German example, BD, I am wondering if replacing "etwas" with a noun with the definite article in accusative is possible.

Sure. Er lehrt sie die Aussprache der deutschen Städte. He teaches her the pronunciation of the German towns. Which could also be rendered with the verb beibringen, but then you'd have your regular dative plus accusative: Er bringt ihr die Aussprache der deutschen Städte bei.

This accusative talk reminds me that it is possible in German, as well as in many other languages, among them English (only Germanic and Romance?), to have a subject in the accusative form after causative and sense verbs:

1b is slightly awkward but still grammatical, whereas 2b is a very bad sentence. The only way to salvage the extraposed "me" is to create a prepositional clause by adding "to." Since "me" in sentences 2a-c behaves differently from that of 1a and b, which is a normal accusative, it is safe to say that BD's double-negative is not two accusatives completely the same in syntactic functionality governed by the same verb.

By the way, what does bei in "Er bringt ihr die Aussprache der deutschen Städte bei" govern, assuming it is a preposition?

Well, bei can indeed be a preposition, but there it functions just like a particle to form phrasal verbs: bringen (to bring), abbringen (to dissuade), anbringen (to fasten; to display; to use), beibringen (to teach), herausbringen (to bring up), wegbringen (to take out). What is going on in German is that these particles have to be detached from the verb in main clauses with a verb in the present, imperative or preterite.

Brazilian dude wrote:This accusative talk reminds me that it is possible in German, as well as in many other languages, among them English (only Germanic and Romance?), to have a subject in the accusative form after causative and sense verbs:

That's Object-to-Subject raising, quite a universal phenomenon found in languages like Japanese.

E.g.,わたしは彼(を/は)馬鹿だと思った。
Gross: I thought him to be an idiot.

When accusative particle o- is used, kare (he) is raised from the subject position for being stupid to the object position for thinking.